Definitely not. UG tabs are good enough, unless you want some uncommon songs that aren't on here.
only if they are official, ive seen a ton of tab books that are incorrect.

if the band had nothing to do with the book its probably got a lot of parts wrong but if its like the dethklok tab book that brendon small did himself than yea.
And if you can't find them here, i doubt you'll find them somewhere else... + for free
most "official" books are deemed "official" because they are written by a "professional" musician, not nessecarilly the artist. and even a lot that say they're by the artist are just approved by the artist and still written by someone else. On top of this they are often not correct or the about the same and in some cases exactly what you will find on this site. Anyhow, if you want free, generally correct tabs this is the best spot i have found.